Cal Trans closed the road to the top and the Lick Observatory is closed for the day, too. But that didn't stop some people. "Right now it's really cold. I'm not used to it. I can hardly feel my hands right now," Santa Clara resident Domingo Santos said.

Santos and a large group of his family members came up anyways. They took the opportunity to have a rare Bay Area snowball fight.

"We were supposed to go to Lake Tahoe but something happened. So we have a fake Lake Tahoe here," 10-year-old Matthew Rambac said.

Matt Brooks works at Lick Observatory. Like many employees, he lives on the mountain. "Ya, I'm stoked on it. Very excited," he said. "Snow started last night. I have some guests here and we weren't really expecting it. Woke up, looked outside and everything was covered in snow."

The sudden change of weather was a surprise for his friends visiting from Arizona. "We came to California not expecting snow," Phoenix resident Connor McBarron said. "So my feet are wet and I'm pretty cold but this has been pretty cool."

There has been a mix of rain and snow flurries throughout the day. It's sticking to trees and there's a couple inches on the ground, turning the area into a winter wonderland -- a treat for families starting the new year.